Radio anatomical analysis of positional relation between anterior ethmoid artery canal and ethmoid skull base in correlation with olfactory fossa

Abstract

Skull base (SB) injuries happens mostly either in the thinnest or the least resistant part of skull base. The lateral lamella of cribriform plate is one of the common sites of injury during endoscopic anterior skull base surgeries. The anterior ethmoid artery (AEA) visualization is considered as a significant anatomical landmark in such surgeries. Studies correlating their positional relation with morphology of olfactory fossa remains limited. This study aims to look into the relation of AEA to that of SB in different types of olfactory fossa morphology. A retrospective radiological study was done on 100 coronal CT images from patients who were subjected to paranasal CT imaging. In bone window of coronal CT scans, the position of AEA in relation to SB was noted and the vertical distance between them was measured. Based on the distance of AEA from SB, 3 groups were subdivided as follows: Group A - < 2.5 mm, Group B – 2.5 to 5 mm and Group C - > 5 mm. The depth of the olfactory fossa was measured and categorized according to Keros classification. Out of 200 sides, AEA was found below SB in 167 out of 200 (83.5%) with majority belonging to Group A (101 out of 167). Keros type II was commonly observed among all the groups. The position of AEA below SB was seen at a greater frequency as the height of SB increased with the Keros classification and was statistically significant (P = .006) The knowledge of presence of anterior ethmoid artery outside the skull base with long lateral lamella preoperatively would help the surgeon to avoid intraoperative complications during endoscopic skull base or sinus surgeries.